According to the Internet specification RFC 2822, an email address must have a single "@" sign. For example, john@host.net is a valid email address.

There should be at least one character before the "@" sign, but the total number of characters before the "@" sign should not be more than 64.

There should be at least one character after the "@" sign, but the total number of characters after the "@" sign should not be more than 255.

How to write a single regular expression to validate all rules listed above?

✍: FYIcenter.com

A

Here is the regular expression for email address @ sign validation:

^[^@]{1,64}@[^@]{1,255}$
^ - begin of the string
[^@] - any character other than @
{1,64} - repeating 1 or up to 64 times
@ - match @ itself
[^@] - any character other than @
{1,255} - repeating 1 or up to 255 times
$ - end of the string